according to the statistics of relevant departments, the sales of sensors in China in 29 was 32.7 billion yuan, of which temperature sensors accounted for 14% of the whole sensor market, which were mainly used in communication electronic products, household appliances, building automation, medical equipment, instrumentation, automotive electronics and other fields.
bimetallic thermometer TBI with sanitary clamp process connection is used for temperature measurement in sanitary application.
(Image source: Baomeng Company)
Characteristics of temperature sensor
As an ideal temperature sensor, it should have the following requirements: wide measuring range, high precision, good reliability, small time drift, light weight, fast response, low price and mass production. However, there is no temperature sensor that meets the above conditions at the same time, and various temperature sensors should be used flexibly according to the application site. This is because different temperature sensors have different characteristics.
● The measuring range and characteristics of different temperature sensors are different.
the temperature measuring range and characteristics of several important types of temperature sensors are shown in table 1.
Table 1. Classification Table of Temperature Sensor and Temperature Range
● The accuracy of temperature measurement is related to the measurement method.
according to the usage methods of temperature sensors, they are usually divided into contact measurement and non-contact measurement. the characteristics of the two measurement methods are shown in table 2.
Table 2 Comparison between contact measurement and non-contact measurement
● Different measuring circuits should be used for different temperature measuring elements.
there are three commonly used measuring circuits. "Resistance temperature measuring element measuring circuit", which should consider eliminating the influence of nonlinear error and thermal resistance wire on measurement accuracy. "Measurement circuit of potential temperature measuring element", which needs to consider linearization and cold end compensation, and the signal processing circuit is more complicated than thermal resistance. The semiconductor integrated temperature sensor is the most typical current-type temperature measuring element. When the power supply voltage changes and the external conductor changes, the output current of the circuit is basically unaffected, which is very suitable for long-distance temperature measurement.
The latest development of temperature measurement
● Develop temperature measuring elements and sensors suitable for various industrial applications.
The platinum film temperature sensor has a thickness of 1μm, and can be placed in a very small measuring space to measure the temperature field distribution. The response time is less than 1ms, the minimum diameter of the thermocouple is 25μm, the thermocouple volume is less than 1×1-4mm3, and the mass is less than 1 μ g..
The multi-color colorimetric temperature sensor can obtain the approximate emissivity of the measured object in real time, and improve the accuracy of radiation temperature measurement.
the temperature resolution of the resonant Shi Ying tuning fork temperature sensor can reach .9℃, the accuracy can reach .2℃, the measuring range can reach-2 ~ 26℃, and the linearity can reach .1 ~ .5%.
The new temperature control device composed of Z-element has the characteristics of simple circuit structure, high precision, high speed, low power consumption and low cost.
The integrated temperature sensor is made of diffused silicon technology, which is suitable for mass production with good consistency and sensitivity of 11.3/℃.
W-Re temperature sensor the high temperature sensor made of W-Re thermocouple can detect the upper limit temperature of 23℃, which is suitable for high temperature measurement in reducing, inert, vacuum, nuclear radiation and other environments.
Intelligent temperature sensor uses MEMS technology to combine typical temperature measuring elements, signal conditioning circuit and microprocessor with digital bus interface into a whole to form an intelligent temperature sensor system.
● The temperature measurement technology has developed from "wired" to "wireless".
traditional temperature measurement usually adopts wired connection with cables, but for some occasions, such as temperature measurement of rotating or moving objects, places where people can't get involved in harsh environment, and environments where wired is not suitable, with the application of intelligent temperature sensors and the consideration of saving wiring cost, temperature measurement technology begins to develop from "wired" to "wireless".
The wireless temperature measurement virtual instrument system using passive surface acoustic wave resonator introduces signal processing method and feedback control, which reduces the system cost, improves the measurement accuracy and distance. Combined with the general computer platform and data I/O board, it is flexibly controlled by software, which can automatically adjust the measurement parameters according to different environments and measurement processes and realize adaptive detection. When the transmission power is 1mW and the wireless detection distance is 4m, the uncertainty of repeated measurement of resonance frequency is about .9kHz, and the uncertainty of temperature measurement sensitivity at 3m is about .1℃.
temperature and humidity sensor system for air conditioning. The system has two parts: main unit and extension unit. The extension regularly transmits the data measured by the temperature and humidity sensors placed inside to the host computer in a wireless way. The host computer converts it into an electrical signal through the output unit and sends it to the control device. Because the extension is powered by battery, it can be placed anywhere, and the control signal is transmitted wirelessly, which is very convenient.
the wireless patrol detection system does not need patrol personnel to visually inspect or record the data measured by the sensors installed on the site, but carries out wireless patrol detection on the sensors with wireless transmission mode through the wireless data collection system. This detection system will be very convenient for the detection of dangerous places and high places.
the method of lengthening thermocouple can be used for deep temperature measurement, but it is extremely inconvenient to use. A special device for deep temperature measurement can be used, which consists of a heater, a metal frame, a thermal insulation layer and a temperature measuring element (such as a thermistor). The principle is that on the surface of the heater, the temperature gradient can be eliminated, and the surface temperature can be measured, so as to know the deep temperature.
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